This invention refers to a display device consisting of a sheet-like support, which is covered with liquid thermocromic crystals, which can be tempered by separate power supply to individual heating element, which lie close to the crystals and are placed between the sheet-like support and the crystals, whereby the crystals assume different shades of colour depending on the given temperature so that hereby the colour of the crystals will form a certain pattern.
A display arrangement of now mentioned type is disclosed in e.g. U.S. Pat. No. 4,142,782. This display includes a sheet-like metallic support, which has a surface, which is covered with a thin layer of a conventional paint. The layer is in turn covered with areas of a certain thermocromic composition and it may also contain areas of different thermocromic composition. It may also contain areas of further different kind of a thermocromic composition and/or mixtures of the earlier mentioned thermocromic compositions. The areas will normally be created by conventional painting techniques using a coating composition containing a thermocromic compound and an appropriate conventional binder and an appropriate solvent. The composition may further include pigments of any colour or the composition can be colourless. The binder is usually colourless in order not to obscure the colour effects to be formed. It is further described in the patent that the heating of the different areas is carried out by plate-like electrical resistance elements, which are placed between the sheet-like support and the areas of the thermocromic positions. These plate-like electrical resistance elements heat the individual crystals in the different areas to a certain temperature so that the crystals in a specific area assume a certain colour depending on the temperature. According to the above described methods certain areas or certain points are given a certain colour by that the thermocromic crystals, above or in the neighbourhood of a certain heating element are heated. Different patterns will hereby be formed by that the crystals having a certain colour will form a certain pattern. If the display however is subjected to the ambient temperature, one can understand that it may be difficult to control the pattern so it has the wanted design and it can also be difficult to change the pattern from one design to another if the new pattern demands a lower temperature for the individual crystals than the earlier temperature. The temperature of the sheet-like support is thus of great importance and the sheet-like support may assume the ambient temperature, which can be so high that the control of the temperature for the individual electrical element have no effect on the crystals but it is only the ambient temperature which has an effect on the crystals.
The object of the invention is to increase the possibilities to control the tempering of the individual crystals and also protect them from being effected by the ambient temperature and also from mechanical damage. The produced picture on the display shall also be possible to program.
The invention is characterized by the features stated in the following patent claims and a favourable embodiment is described in the following by reference to accompanying drawings.